Continuous Sine Wave Generation

[Keypecker]

I am trying to develop a test program and I need to be able to generate a  continuous sine wave and dynamically change the frequency and amplitude.

I have tried various methods and have attempted to modify a number of the examples that I have found in the library and ni website, all to no avail.

I either get a waveform that is continuous, but must be stopped to make changes, or changes can be made dynamically but the waveform is not

continuous. I am currently using LabVIEW verion 7.1.

In the past I have done this in LabVIEW 6.1, with a buffered traditional vi, but DAQmx does not seem to have a comparable vi in its library. An added

complication is that, while the test circuit is being driven with the sine wave, I also need to be aquiring data to enable me to measure bandwidth and

distortion.

I am sure that, if I could do it in version 6.1, I should be able to achieve it, more easily, in version 7.1 but, at the moment, this does not seem to be the

case.

Please can you assist me in finding a solution.

Thanks.

[ArchivedPointOnePa]

Keypecker wrote:
> I am trying to develop a test program and I need to be able to
> generate a  continuous sine wave and dynamically change the
> frequency and amplitude. I have tried various methods and have
> attempted to modify a number of the examples that I have found in the
> library and ni website, all to no avail. I either get a waveform that
> is continuous, but must be stopped to make changes, or changes can be
> made dynamically but the waveform is not continuous. I am currently
> using LabVIEW verion 7.1. In the past I have done this in LabVIEW
> 6.1, with a buffered traditional vi, but DAQmx does not seem to have
> a comparable vi in its library. An added complication is that, while
> the test circuit is being driven with the sine wave, I also need to
> be aquiring data to enable me to measure bandwidth and distortion. I
> am sure that, if I could do it in version 6.1, I should be able to
> achieve it, more easily, in version 7.1 but, at the moment, this
> does not seem to be the case. Please can you assist me in finding a
> solution.   Thanks.

I'm not sure why this is a problem for you. The typical approach is to use a "phase accumulator" to achieve "Direct Digital Synthesis" (DDS). Search Google or NI for "phase accumulator labview".
I found the following references:

http://digital.ni.com/worldwide/singapore.nsf/web/all/C329DEA919DAA9E48625724600442103

ftp://ftp.ni.com/pub/devzone/pdf/tut_5516.pdf